1. Field of the invention
The present invention relates to a furnace for manufacturing a semiconductor device and a method of forming a gate oxide film by utilizing the same, and particularly, to a furnace for manufacturing a semiconductor device and a method of forming a gate oxide film by utilizing the same which can produce an oxide film of improved characteristics and reduce the required thermal budget by first resolving N.sub.2 O in a source furnace maintained at a high temperature and then oxidizing a selected portion of the wafer by making a N.sub.2 O gas and NH.sub.3 gas react in a main furnace maintained at a low temperature.
2. Information Disclosure Statement
As the degree of integration is increased, the thickness of the gate oxide film which generally forms a MOS device is decreased. A prior art furnace for manufacturing a semiconductor device and a method for forming a gate oxide film by utilizing the same are explained below with reference to FIG. 1 and FIG. 2.
The prior art furnace for manufacturing a semiconductor device is constructed in such a way that wafers 5 loaded in a boat 4 are placed in a furnace 1 provided with a gas inlet 2 and an outlet 3 as shown in FIG. 1. In the method of forming the gate oxide film of the semiconductor device utilizing the furnace 1, the wafer 5 is loaded into the furnace 1 at the temperature of 650.degree. C., and the lamp up process proceeds in such manner that the temperature of the furnace 1 is raised to 700.degree. C. through 900.degree. C. as shown in FIG. 2. Then, the furnace 1 is stabilized under an N.sub.2 gas environment. The gate oxide film is then formed on the wafer 5 by the oxidization process resulting from reaction of N.sub.2 O and NH.sub.3 gases injected through the gas inlet 2. A heat treatment process is then conducted under N.sub.2 gas environment. Then, a ramp down process lowers the temperature of the furnace 1 to 800.degree. C. The wafers 5 are then unloaded.
The resolution temperature of N.sub.2 O gas is above 900.degree. C., and that of NH.sub.3 gas is 600.degree. C. through 700.degree. C., so that the resolution of N.sub.2 O gas is small in the oxidization process. On the other hand, the resolution of NH.sub.3 gas is excessive, thereby reducing the amount of NH.sub.3 gas. If the temperature of the furnace 1 is lowered in the oxidization process to improve the quality of the gate oxide film, the resolution of NH.sub.3 gas is even greater so that the amount of H.sub.2 is increased, creating the danger of explosion, and degrading the quality of the gate oxide film.